The invention relates to connections of tubular components for bicycle frames or forks, particularly steering head, bottom bracket bearing, seat head and center connections, wherein the shaped end section of at least one first tube is connected with the other jacket of a second tube by material injection-molded therearound, and to a method for producing such connections.
Such known connections are used in the manufacture of bicycle frames as a substitute for welded, soldered, screwed or riveted junctions as they are employed, in particular, in the production of sturdy children's bicycles and for folding bicycles as well as for modern aluminum bicycles.
The above-mentioned known connections are produced in a metal injection molding process at the end sections of the individual tubes to be connected, with the end sections of the frame tubes being shaped, for example, in the form of flanges and the open ends are closed off with caps. Although such bicycle frames are relatively strong with respect to static and dynamic loads, they have the drawback that the connections produced in this manner are relatively heavy and thus are not consistent with to the present-day trend in bicycle design, namely to produce a bicycle that is as light in weight as possible.
Another drawback of such a metal injection molding process is the considerable amount of time it requires. Moreover, the injection molding and soldering temperatures involved are very high, i.e. several hundred degrees Celsius. This may cause warping of the finished frames and it becomes necessary to correct the frame and the forks by way of aligning them. Moreover, depending on the selected connection process, the tubular frame sections must not exceed a certain wall thickness and no plastic components can be used for the tubular frame sections.
It is also a drawback that the frame sections cannot be lacquered before the metal injection molded connections are produced; thus, the lacquering process can take place only after the bicycle frame is completed.